package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Follow;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.lang.reflect.Type;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

//并将其创建为一个Bean，放入 Spring容器中进行管理
@Component
@Slf4j
//把解决缓存问题的方法提取到一个工具类中
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }
    public void setWithLogicalExpire(String key, Object value,Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }
    //解决缓存穿透的问题
    public <R,ID> R queryWithPassThrough(String  keyPrefix, ID id, Class<R> type,
                                         Function<ID,R> dbFallback,Long time, TimeUnit unit){
        String key =keyPrefix+id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断缓存是否命中
        if (StrUtil.isNotBlank(json)) {
            //3.命中返回商铺对象
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否为空值
        if(json!=null){
            return null;
        }
        //4.未命中根据id查询数据库
        R r=dbFallback.apply(id);
        if (r == null) {
            //为了防止缓存穿透，要向缓存中添加一个空对象,同时要设置过期时间
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
            //5.判断店铺是否存在
            return null;
        }
        //6,存在将店铺数据写入redis,并设置过期时间
        this.set(key,r,time,unit);
        //返回
        return r;
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    //第二种：利用逻辑过期解决缓存击穿问题
    public  <R,ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type,Function<ID,R> dbFallback,Long time, TimeUnit unit) {
        String key =keyPrefix+id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断缓存是否命中
        if (StrUtil.isBlank(json)) {
            //3.未命中返回null
            return null;
        }

        //4.命中判断是否过期,需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        // 添加空值检查
        if (redisData.getData() == null) {
            return null;
        }
        
        R r= JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期直接返回店铺信息
            return r;
        }
        //5.2已过期,需要缓存重建
        //6.重建缓存
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否取锁成功
        if(isLock){
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺信息
        return r;
    }
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        //防止出现空指针异常
        return BooleanUtil.isTrue(flag);
    }
    //删除锁
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }
}
